Response of Mature Vines of Vitis Labrusca L. CV Concord to Applications of Phosphorus and Potassium over an Eight-Year Span in Pennsylvania

Abstract

Experiments concerned with the application of phosphorus (P) to the soil annually at the rate of 50 kg and 150 kg P/ha over an eight-year duration in combination with nitrogen (NP and NP₃) or nitrogen and potassium (NPK and NP₃K) were conducted in Erie County, Pennsylvania.

Yield, number of clusters per vine, cluster weight, berry weight, vine capacity and fruitfulness per retained node were increased by NK, NPK, and NP₃K treatments. NPK and NP₃K treatments were more effective than NK. Other treatments — N, NP, and NP₃ treatments —either were ineffective or inconsistent. Soluble solids percentage of the juice was reduced by the NPK and NP₃K treatments. However, a negative correlation was found between yield and soluble solids content of the juice (r = -0.8631). Available soil P was increased by P application at 150 kg/ha. Available soil K was increased by K application at 95 kg/ha. Plant analyses revealed that petiole P increased as a result of applying P to the soil. Positive correlations existed between petiole magnesium (Mg) and petiole calcium (Ca); petiole zinc (Zn) and petiole boron (B); number of clusters per vine and yield. Petiole P and petiole Zn were not associated.